1. Field of the Invention
The present invention relates to a reflection type liquid crystal display device and, in particular, to a reflection type liquid crystal device superior in reliability and a method for manufacturing the same.
2. Description of the Related Art
Nowadays, a reflection type liquid crystal display device, which consumes relatively little power and which can be made small in thickness, is widely used as the display portion of a hand-held type computer or the like.
A known example of the reflection type liquid crystal display device is an outside type in which a reflection plate is arranged outside a pair of substrates provided on either side of a liquid crystal layer. However, in an outside type reflection type liquid crystal display device, the light entering the reflection type liquid crystal display device is reflected by a reflection film of the reflection plate after passing the two substrates, with the result that the bright display is rather dark.
To cope with this problem, there has been proposed a built-in type reflection type liquid crystal display device, in which there is arranged between a pair of substrates a reflection film whose surface is a mirror surface, and in which light is passed through only one substrate. However, in this reflection type liquid crystal display device, it is difficult to effectively utilize light, so that the contrast is rather low.
To eliminate this problem, there exists a built-in type reflection type liquid crystal display device as shown in FIG. 13, in which the metal reflection film for reflecting light has protrusions and recesses. In FIG. 13, numeral 1a indicates a first substrate, and FIG. 1b indicates a second substrate. On the surface of the second substrate 1b opposed to the first substrate 1a, there are formed second electrode layers 9b and a second orientation film 4b, and on the surface on the opposite side, a phase plate 5 and a polarizing plate 6 are sequentially stacked one upon the other. On the other hand, on the surface of the first substrate 1a opposed to the second substrate 1b, an organic film 44 having a large number of protrusions and recesses, a metal reflection film 54, an overcoat film 64, a first electrode layer 94a, and a first orientation film 4a are sequentially stacked one upon the other. The overcoat layer 64 is provided in order to flatten out the protrusions and recesses of the metal reflection layer 54, and to insulate the metal reflection film 54 from the electrode layer 94a. A liquid crystal layer 2 is sealed in the space surrounded the first substrate 1a and the second substrate 1b, having the above-mentioned layers, and a seal material held between them.
FIG. 14 is a plan view of the reflection type liquid crystal display device shown in FIG. 13, with the second substrate, the layers provided on the sides of the second substrate, the liquid crystal layer, the seal material, and the first orientation film being omitted. In FIGS. 13 and 14, numeral 7 indicates a driving element mounting region, and numeral 8 indicates a display region. Here, the driving element mounting region 7 is a region where a driving element is mounted, and the display region is a region used for the display of the liquid crystal display device.
As shown in FIGS. 13 and 14, on the overcoat film 64 of the driving element mounting region 7, there is mounted a driving element 16 through the intermediation of an anisotropic conductive film 10 (hereinafter referred to as "ACF" having a conductive filler 10a. The ACF 10 has a conductive filler 10a, and conductivity can be imparted thereto by heating and pressurizing it.
The first electrode layer 94a of the driving element mounting region 7 connected to the display region 8 is electrically connected to one terminal 11a of the driving element 16 through the intermediation of the ACF 10. Further, the other terminal 11b of t he driving element 16 is connected to the first electrode layer 94c through the intermediation of the ACF 10.
In this reflection type liquid crystal display device, to stack the organic film 44, the metal reflection film 54, and the overcoat film 64 on the surface of the first substrate 1a, a photosensitive resin liquid is first applied, as shown in FIG. 15, to the first substrate 1a, which consists of a transparent glass plate or the like, and this photosensitive resin liquid is pre-baked to form a photosensitive resin layer 44a. Next, the pattern surface of a transfer pattern 14 having a flat portion 14a in the periphery is pressed against the photosensitive resin layer 44a on the first substrate la for a fixed period of time to transfer the protrusions of the transfer pattern 14 to the surface of the photosensitive resin layer 44a of the display region 8 shown in FIG. 15, and, as shown in FIG. 16, a large number of protrusions are formed. After this, rays 20 such as ultraviolet rays (g, h and i-rays) are applied to the whole from the back side (the lower side as seen in the drawing) of the first substrate to cure the photosensitive resin layer 44b having a large number of protrusions and recesses. After this, the transfer pattern 14 is detached from the photosensitive resin layer 44b, and post-baking is performed to obtain the organic film 44 as shown in FIG. 17. Then, aluminum, silver or the like is vapor deposited on the display region 8 of the organic film 44 to form the metal reflection layer 54 as shown in FIG. 18. After this, the overcoat film 64 shown in FIG. 19 is formed by a thermosetting acrylic resin or the like.
As shown in FIG. 13, in this reflection type liquid crystal display device, the organic film 44, the overcoat film 64, the ACF 10, and the first electrode layers 94a and 94c are provided between the driving element 16 and the first substrate 1a. Being formed of an organic substance, the organic film 44 is very soft. Thus, there is a fear that the terminals 11a and 11b of the driving element 16 will sink in to generate cracks in the first electrode layers 94a and 94c when the driving element 16 is electrically connected to the first electrode layers 94a and 94c by heating and pressurizing the ACF 10. Further, due to the cracks, there is a fear that the first electrode layers 94a and 94c will suffer a break.
Further, it is difficult to bring the organic film 44 formed of a photosensitive resin into close contact with the first substrate 1a consisting of a glass plate. In particular, in the portion where it is exposed to the atmospheric air at the end surface of the reflection type liquid crystal display device, the organic film 44 takes up moisture, so that it is more liable to separation.